diff mbox series

[v2,4/4] serial: qcom_geni: Use devm_krealloc_array

Message ID 20230309150334.216760-5-james.clark@arm.com
State New
Headers show
Series devres: Provide krealloc_array | expand

Commit Message

James Clark March 9, 2023, 3:03 p.m. UTC
Now that it exists, use it instead of doing the multiplication manually.

Signed-off-by: James Clark <james.clark@arm.com>
---
 drivers/tty/serial/qcom_geni_serial.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Jonathan Cameron March 11, 2023, 7:18 p.m. UTC | #1
On Thu,  9 Mar 2023 15:03:33 +0000
James Clark <james.clark@arm.com> wrote:

> Now that it exists, use it instead of doing the multiplication manually.
> 
> Signed-off-by: James Clark <james.clark@arm.com>

Hmm. I've stared at the users of this for a bit, and it's not actually obvious
that it's being used as an array of u32.  The only typed user of this is as
the 2nd parameter of  
tty_insert_flip_string() which is an unsigned char *

I wonder if that sizeof(u32) isn't a 'correct' description of where the 4 is coming
from even if it has the right value?  Perhaps the fifo depth is just a multiple of 4?

Jonathan



> ---
>  drivers/tty/serial/qcom_geni_serial.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index d69592e5e2ec..23fc33d182ac 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -1056,9 +1056,9 @@ static int setup_fifos(struct qcom_geni_serial_port *port)
>  		(port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE;
>  
>  	if (port->rx_buf && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) {
> -		port->rx_buf = devm_krealloc(uport->dev, port->rx_buf,
> -					     port->rx_fifo_depth * sizeof(u32),
> -					     GFP_KERNEL);
> +		port->rx_buf = devm_krealloc_array(uport->dev, port->rx_buf,
> +						   port->rx_fifo_depth, sizeof(u32),
> +						   GFP_KERNEL);
>  		if (!port->rx_buf)
>  			return -ENOMEM;
>  	}
James Clark March 17, 2023, 11:34 a.m. UTC | #2
On 11/03/2023 19:18, Jonathan Cameron wrote:
> On Thu,  9 Mar 2023 15:03:33 +0000
> James Clark <james.clark@arm.com> wrote:
> 
>> Now that it exists, use it instead of doing the multiplication manually.
>>
>> Signed-off-by: James Clark <james.clark@arm.com>
> 
> Hmm. I've stared at the users of this for a bit, and it's not actually obvious
> that it's being used as an array of u32.  The only typed user of this is as
> the 2nd parameter of  
> tty_insert_flip_string() which is an unsigned char *
> 
> I wonder if that sizeof(u32) isn't a 'correct' description of where the 4 is coming
> from even if it has the right value?  Perhaps the fifo depth is just a multiple of 4?
> 
> Jonathan
> 

The commit that added it (b8caf69a6946) seems to hint that something
reads from it in words. And I see this:

  /* We always configure 4 bytes per FIFO word */
  #define BYTES_PER_FIFO_WORD		4U

Perhaps sizeof(u32) isn't as accurate of a description as using
BYTES_PER_FIFO_WORD but I'd be reluctant to make a change because I
don't really understand the implications.

There is also this in handle_rx_console():

  unsigned char buf[sizeof(u32)];

James

> 
> 
>> ---
>>  drivers/tty/serial/qcom_geni_serial.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
>> index d69592e5e2ec..23fc33d182ac 100644
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -1056,9 +1056,9 @@ static int setup_fifos(struct qcom_geni_serial_port *port)
>>  		(port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE;
>>  
>>  	if (port->rx_buf && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) {
>> -		port->rx_buf = devm_krealloc(uport->dev, port->rx_buf,
>> -					     port->rx_fifo_depth * sizeof(u32),
>> -					     GFP_KERNEL);
>> +		port->rx_buf = devm_krealloc_array(uport->dev, port->rx_buf,
>> +						   port->rx_fifo_depth, sizeof(u32),
>> +						   GFP_KERNEL);
>>  		if (!port->rx_buf)
>>  			return -ENOMEM;
>>  	}
>
Jonathan Cameron March 18, 2023, 5:34 p.m. UTC | #3
On Fri, 17 Mar 2023 11:34:49 +0000
James Clark <james.clark@arm.com> wrote:

> On 11/03/2023 19:18, Jonathan Cameron wrote:
> > On Thu,  9 Mar 2023 15:03:33 +0000
> > James Clark <james.clark@arm.com> wrote:
> >   
> >> Now that it exists, use it instead of doing the multiplication manually.
> >>
> >> Signed-off-by: James Clark <james.clark@arm.com>  
> > 
> > Hmm. I've stared at the users of this for a bit, and it's not actually obvious
> > that it's being used as an array of u32.  The only typed user of this is as
> > the 2nd parameter of  
> > tty_insert_flip_string() which is an unsigned char *
> > 
> > I wonder if that sizeof(u32) isn't a 'correct' description of where the 4 is coming
> > from even if it has the right value?  Perhaps the fifo depth is just a multiple of 4?
> > 
> > Jonathan
> >   
> 
> The commit that added it (b8caf69a6946) seems to hint that something
> reads from it in words. And I see this:
> 
>   /* We always configure 4 bytes per FIFO word */
>   #define BYTES_PER_FIFO_WORD		4U
> 
> Perhaps sizeof(u32) isn't as accurate of a description as using
> BYTES_PER_FIFO_WORD but I'd be reluctant to make a change because I
> don't really understand the implications.

Agreed with your analysis.  + fully understand why you don't want to change
it. 

I'd be tempted to take the view that whilst it's allocated in 4 byte chunks
because it's accessed elsewhere as a set of 1 byte entries, krealloc_array
isn't appropriate and so just leave it with devm_krealloc()

Risk is that a steady stream of patches will turn up 'fixing' this as
it will be easy for people to find with a script.  Maybe better to just add
a comment (either with or without your patch).
> 
> There is also this in handle_rx_console():
> 
>   unsigned char buf[sizeof(u32)];
> 
> James
> 
> > 
> >   
> >> ---
> >>  drivers/tty/serial/qcom_geni_serial.c | 6 +++---
> >>  1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> >> index d69592e5e2ec..23fc33d182ac 100644
> >> --- a/drivers/tty/serial/qcom_geni_serial.c
> >> +++ b/drivers/tty/serial/qcom_geni_serial.c
> >> @@ -1056,9 +1056,9 @@ static int setup_fifos(struct qcom_geni_serial_port *port)
> >>  		(port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE;
> >>  
> >>  	if (port->rx_buf && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) {
> >> -		port->rx_buf = devm_krealloc(uport->dev, port->rx_buf,
> >> -					     port->rx_fifo_depth * sizeof(u32),
> >> -					     GFP_KERNEL);
> >> +		port->rx_buf = devm_krealloc_array(uport->dev, port->rx_buf,
> >> +						   port->rx_fifo_depth, sizeof(u32),
> >> +						   GFP_KERNEL);
> >>  		if (!port->rx_buf)
> >>  			return -ENOMEM;
> >>  	}  
> >
diff mbox series

Patch

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index d69592e5e2ec..23fc33d182ac 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1056,9 +1056,9 @@  static int setup_fifos(struct qcom_geni_serial_port *port)
 		(port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE;
 
 	if (port->rx_buf && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) {
-		port->rx_buf = devm_krealloc(uport->dev, port->rx_buf,
-					     port->rx_fifo_depth * sizeof(u32),
-					     GFP_KERNEL);
+		port->rx_buf = devm_krealloc_array(uport->dev, port->rx_buf,
+						   port->rx_fifo_depth, sizeof(u32),
+						   GFP_KERNEL);
 		if (!port->rx_buf)
 			return -ENOMEM;
 	}